Gastric bypass surgery may cut the risk of bowel cancer

A common form of weight loss surgery can reduce the risk of colorectal cancer by modifying the levels of molecules called bile acids in the blood and the small intestine. The results could lead to new treatments for intestine cancer.

Gastric bridging surgery involves storing the stomach to form a small upper pocket and a larger lower pocket. The small intestine is then connected to the upper pocket so that the digestive foods and juices by the most part of the stomach and the start of the small intestine. After the operation, people generally feel earlier and lose weight.

Previous studies have also linked the procedure to a reduced risk of colorectal cancer, but we did not know why. To find out, Rebecca Kesselring at the University of Freiburg in Germany and his colleagues fed mice a diet rich in fat until they earn an average of their initial body weight on average. They then gave a third of gastric mouse surgery while the rest has undergone simulated surgery which did not reorganize their digestive organs.

Aiming to isolate the effect of having gastric puncture surgery from that of weight loss, the team put the gastric bypass group and half of the remaining mice on a diet that made them lose about a fifth of their weight, on average, more than six weeks.

The researchers then set up colorectal cancer cells in the mouse settlers. After six weeks, they found that the colon tumors in the gastric bridging group were two thirds smaller than those of the mice who had continued to gain weight or the mice that had lost weight by the single diet.

In addition, the tumors had spread to the liver in one out of 20 mouse in the gastric bristing group, while this happened in most animals in simulated groups.

“As the two dummy groups had similar levels of tumors but different weights, weight loss itself did not represent the risk of reduced cancer – there was something else about bridging surgery,” explains Kesselring.

The team wondered if changes in bile acids, a mixture of molecules that digest fat, could be responsible. These are generally made by the liver and cross the gallbladder, the stomach and the small intestine before turning into the liver via blood.

“With bridging surgery, bile acids are introduced later into the small intestine,” explains Kesselring. This means that they can meet a different mixture of intestinal bacteria, which chemically modify the molecules.

The mice which underwent gastric surgery had a reduction in the levels of certain bile acids called primary bile acids in their settlers and blood compared to those of simulated groups.

To test whether the changes in bile acid have really changed the risk of cancer, the team put another mouse group through the same experience – but instead of gastric surgery, these mice had an operation that simply diverted their bile acids to a later part of their small intestine without modifying the stomach.

Above all, the team found that this reduced primary bile acid levels in the blood and reduced the size and propagation of colorectal tumors in these mice as effectively as gastric bridging. This was supported by another experience where the team found that primary bile acids strengthen the growth of colorectal cancer cells in a laboratory dish.

The results suggest that targeting primary bile acids could help treat cancer. “We may understand an oral drug that reduces these bile acids, which we could give people with cancer, to simulate some of these beneficial effects of [gastric bypass] Surgery, ”explains Vance Albaugh to Louisiana State University.